Real-time image data access from virtual memory in a digital printing system

Abstract

In a real-time printing system, in which large blocks of digital data corresponding to page images must be located in a memory via a translation table and accessed from the memory within a very narrow time frame, the memory-management internal program of an operating system is overridden by external instructions which lock the translation table in memory.

We claim: 
     
       1. A method of accessing data stored in a memory, the memory having real addresses and virtual addresses associated therewith, the memory being controlled by an operating system, the operating system responding to external commands and having internal commands associated therewith, comprising the steps of: generating a translation table showing relationships between real addresses and virtual addresses in the memory;   causing the translation table to be retained in the memory; and   providing to the operating system an external command causing the operating system to begin executing an internal command to lock a portion of the translation table in the memory;   wherein the operating system is a UNIX operating system and the external command causes the operating system to begin executing an "as --  fault(in)" internal command the external command prevents an "as --  fault(in)" internal command from being automatically executed by the operating system.   
     
     
       2. A method of accessing data stored in a memory, the memory having real addresses and virtual addresses associated therewith, the memory being controlled by an operating system, the operating system responding to external commands and having internal commands associated therewith, comprising the steps of: generating a translation table showing relationships between real addresses and virtual addresses in the memory;   causing the translation table to be retained in the memory; and   providing to the operating system an external command causing the operating system to begin executing an internal command to lock a portion of the translation table in the memory;   wherein the external command causes the operating system not to permit over-writing a portion of the translation table without a further external command and the operating system is a UNIX operating system and the external command prevents an "as --  fault(out)" internal command from being automatically executed by the operating system.